On 23/04/2016 19:31, Tim Lamb wrote:
In message , Brian-Gaff
writes
Well, does this mean that it is only proof against flameless explosions
then?

Long time ago now, Brian.

The few weeks I spent as an apprentice transiting through the
*flameproof* control gear dept. left me believing the equipment was
intended to operate safely in an *explosive* environment.

Coal mines or refineries where explosive gas mixes were likely. The
principle was to prevent an explosion caused by switchgear filled with
gas igniting the surroundings. Achieved by using a thick cast metal
housing with a narrow gap to absorb the energy from an internal flame.

That's it, EEx d. The flame path (the gap between the box and lid for
instance) is long enough and narrow enough that although an explosive
atmosphere may leak in and be ignited by electrical equipment in the box
the resultant release through the gap is slowed and will have cooled
enough that it cannot ignite the atmosphere outside the box.

Enclosures can be certified for explosive gases, explosive dusts or both.